1. Field of the Invention
The present invention relates to a backlight device, and a display device including a liquid crystal element, provided with the backlight device.
2. Description of the Related Art
Nowadays, a liquid crystal display device is used in a wide range of fields such as a liquid crystal television, a PDA, a mobile phone, and office automation equipment like a personal computer, as well as a clock and a calculator.
In a liquid crystal display device, liquid crystal is sealed between two light-transmitting substrates. When voltage is applied, a direction of liquid crystal molecules is changed and light transmittance thereof is changed, so that a predetermined image or the like is displayed optically. Since liquid crystal does not emit light by itself, a backlight unit serving as a light source is provided on the back of a liquid crystal display panel. The backlight unit includes a light source, a light guide plate, a reflective film, a prism film, a diffusing film, and the like, and supplies light to display an image or the like to the entire surface of the liquid crystal display panel uniformly.
As the light source in the backlight unit, a cold cathode fluorescent lamp in which mercury or xenon is sealed in a fluorescent tube is generally used.
A light source in a backlight device as described above has luminance which changes according to an ambient temperature and there is a case such that luminance of the light source is decreased because of rise in temperature due to its own heat generation. Therefore, in order to make a temperature of the light source an optimum driving temperature, a measure for releasing heat such as a heat sink, a heat pipe, or air cool by a cooling fan is tried. As one of measures for releasing heat, a method in which a fluorescent tube has a Peltier element and cooling is carried out by the Peltier element is given (for example, see Patent Document 1: Japanese Published Patent Application No. H6-324304 and Patent Document 2: Japanese Published Patent Application No. H7475035).